Verifying a road network of a map

ABSTRACT

The present disclosure relates to a computer implemented method, a computer program product, and a computer system for verifying the road network of map. An embodiment of the present invention provides a method for verifying a road network of a map. The method comprises: determining, based on locations of a set of points in the map, a trajectory distance of a trajectory between a start point and an end point in the set of points on the map; determining a route distance between the start point and the end point in the road network of the map; and verifying the road network by comparing the trajectory distance and the route distance.

BACKGROUND

The present invention generally relates to a computer implementedmethod, a computer program product, and a computer system for verifyinga road network of a map, and more specifically to continuously improvingthe road network of a map.

In various fields such as connected vehicle, intelligent transportationor location-based service (LBS), a map provides fundamental informationto support other services. In particular, a road network of a map may beused to provide information regarding roads and traffic lines.Currently, the quality of free maps is rather poor. Traditionally, usershave to pay for high-quality road network data (purchased in data lump,or purchased by use time), which restricts common users use of a roadnetwork.

It has been proposed to generate a road network using location datacollected by the positioning systems of vehicles or mobile devices.Meanwhile, some non-commercial third-party map providers also provideroad network services. However, a common problem for these road networkslies in low accuracy. Due to restrictions in various aspects such asdevice, cost, policy, data collection, road network generation for afree map may have limited accuracy. Therefore, the road network data ofmany currently available maps may be problematic. Two most common roadnetwork errors are road segment missing error and road segmentconnectivity error. A road segment missing error means a route in thereal world is not correctly reflected on the map, while a road segmentconnectivity error means connectivity between road segments on the maphas a deviation from the actual roads. The road network in the map mayalso have other types of errors.

Inaccurate road network may cause inconvenience to a user. For example,if one or more road segments indicated in the road network do not exist,the user would have to reselect a route during traveling, which not onlywastes the user's time, but also might cause a traffic problem, or asecurity risk. On the contrary, if a road segment existing in the realworld is not reflected in the road network, it likely wastes the user'stime and resources, and the user has to modify their route.

SUMMARY

In general, embodiments of the present invention provide a technicalsolution for verifying a road network of a map.

In an aspect, an embodiment of the present invention provides a methodfor verifying a road network of a map. The method includes determining,based on locations of a set of points in the map, a trajectory distanceof a trajectory between a start point and an end point in the set ofpoints on the map; determining a route distance between the start pointand the end point in the road network of the map; and verifying the roadnetwork by comparing the trajectory distance and the route distance.

In another aspect, an embodiment of the present invention provides asystem for verifying a road network of a map. The system includes atrajectory distance determining unit configured to determine, based onlocations of a set of points in the map, a trajectory distance of atrajectory between a start point and an end point in the set of pointson the map; a route path determining unit configured to determine aroute distance between the start point and the end point in the roadnetwork of the map; and a road network verifying unit configured toverify the road network by comparing the trajectory distance and theroute distance.

According to an embodiment of the present invention, a plurality ofcontinuous locations in a moving trajectory of a vehicle or a user aremapped to a set of points on the map. A distance between two points maybe determined based on distribution locations on points in the set ofpoints. Meanwhile, a route path between the two points may be determinedbased on map-based road network information. By appropriately computinga deviation between the road network information and the actualtrajectory information based on the two distances, a potential error inthe road network may be effectively identified. Other features andadvantages of the present invention may become easily comprehensiblethrough the description infra.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Through the more detailed description of some embodiments of the presentdisclosure in the accompanying drawings, the above and other objects,features and advantages of the present disclosure will become moreapparent, wherein:

FIG. 1 shows an exemplary computer system/server which is applicable toimplement an embodiment of the present invention;

FIG. 2 shows a schematic flow diagram of a method for verifying a roadnetwork of a map according to an embodiment of the present invention;

FIG. 3 shows a schematic diagram of checking a road segment connectivityerror in a road network of a map according to an embodiment of thepresent invention;

FIG. 4 shows a schematic diagram of checking a missing road segment in aroad network of a map according to an embodiment of the presentinvention; and

FIG. 5 shows a schematic block diagram of a system for verifying a roadnetwork of a map according to an embodiment of the present invention.

In respective figures, same or like reference numerals are used torepresent the same or like components.

DETAILED DESCRIPTION

Some preferable embodiments will be described in more detail withreference to the accompanying drawings, where the preferable embodimentsof the present disclosure have been illustrated. However, the presentdisclosure can be implemented in various manners, and thus should not beconstrued to be limited to the embodiments disclosed herein. On thecontrary, those embodiments are provided for the thorough and completeunderstanding of the present disclosure, and completely conveying thescope of the present disclosure to those skilled in the art.

Referring now to FIG. 1, in which an exemplary computer system/server 12which is applicable to implement an embodiment of the present inventionis shown. Computer system/server 12 is only illustrative and is notintended to suggest any limitation as to the scope of use orfunctionality of embodiments of the invention described herein.

As shown in FIG. 1, a computer system/server 12 is shown in the form ofa general-purpose computing device. The components of the computersystem/server 12 may include, but are not limited to, one or moreprocessors or processing units 16, a system memory 28, and a bus 18 thatcouples various system components including the system memory 28 to theprocessor 16.

The bus 18 represents one or more of any of several types of busstructures, including a memory bus or a memory controller, a peripheralbus, an accelerated graphics port, and a processor or local bus usingany of a variety of bus architectures. By way of example, and notlimitation, such architectures include Industry Standard Architecture(ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA)bus, Video Electronics Standards Association (VESA) local bus, andPeripheral Component Interconnect (PCI) bus.

The computer system/server 12 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by the computer system/server 12, and may include bothvolatile and non-volatile media, removable and non-removable media.

The system memory 28 may include computer system readable media in theform of volatile memory, such as random access memory (RAM) 30 and/orcache memory 32. The computer system/server 12 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, a storage system 34 may be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to the bus 18 by one or moredata media interfaces. As will be further depicted and described below,the system memory 28 may include at least one program product having aset (e.g., at least one) of program modules that are configured to carryout the functions of embodiments of the invention.

A program/utility 40, having a set (at least one) of a program module42, may be stored in the system memory 28 by way of example, and notlimitation, as well as an operating system, one or more applicationprograms, other program modules, and program data. Each of the operatingsystems, one or more application programs, other program modules, andprogram data or some combination thereof, may include an implementationof a networking environment. The program modules 42 generally carriesout the functions and/or methodologies of an embodiment of the inventionas described herein.

The computer system/server 12 may also communicate with one or moreexternal devices 14 such as a keyboard, a pointing device, a display 24,etc.; one or more devices that enable a user to interact with thecomputer system/server 12; and/or any devices (e.g., network card,modem, etc.) that enable the computer system/server 12 to communicatewith one or more other computing devices. Such communication can occurvia an Input/Output (I/O) interface 22. Still yet, the computersystem/server 12 can communicate with one or more networks such as alocal area network (LAN), a general wide area network (WAN), and/or apublic network (e.g., the Internet) via a network adapter 20. Asdepicted, the network adapter 20 communicates with the other componentsof the computer system/server 12 via the bus 18. It should be understoodthat although not shown, other hardware and/or software components couldbe used in conjunction with the computer system/server 12. Examples,include, but are not limited to: microcode, device drivers, redundantprocessing units, external disk drive arrays, RAID systems, tape drives,and data archival storage systems, etc.

Hereinafter, the mechanism and principle of an embodiment of the presentinvention will be described in detail. Unless otherwise stated, the term“based on” used hereinafter and in the claims expresses “at leastpartially based on.” The term “comprise” or “include” or a similarexpression indicates an open inclusion, i.e., “including, but notlimited to . . . .” The term “plural” or a similar expression indicates“two or more.” The term “one embodiment” indicates “at least oneembodiment.” The term “another embodiment” indicates “at least oneanother embodiment.” Definitions of other terms will be provided in thedescription infra.

FIG. 2 shows a flow diagram of a method 200 for verifying a road networkof a map according to an embodiment of the present invention. The method200 begins at step S210, where a distance of a trajectory between astarting point and an end point in the set of points is determined basedon locations of a set of points on the map. For the convenience ofdiscussion, the distance is called the “trajectory distance.”

According to an embodiment of the present invention, the points in a setof points processed at step s210 correspond to a trajectory. Such set ofpoints can be obtained in various manners. For example, in anembodiment, the set of points are obtained by mapping a group oflocations as sensed onto a map to be verified. The group of locationsmay be sensed by any appropriate positioning technique. For example, inan embodiment, the location data of the set of points on the trajectorymay be collected continuously or periodically during travel of a vehicleor a user using a positioning device equipped on the vehicle or on themobile device of the user. Examples of the positioning devices include,but not limited to, at least one of the following: a GPS (globalpositioning system) receiver, a Galileo positioning system receiver, aBeidou positioning system receiver, etc. In an embodiment, location dataof the respective points in the trajectory may be collected by the samevehicle or user. Alternatively, in another embodiment, location datacollected by multiple vehicles and/or users may also be used to form thetrajectory.

The location data may be mapped to the map by coordinate transformation.In particular, in an embodiment, these locations may be mapped to pointson the map using a map matching technology. As known, the match matchingtechnology may match each mapped point to a particular road segment inthe network. Moreover, the map matching technology may provide a matchdegree between the matched respective point and the corresponding roadsegment. During the process of performing road matching, additionalprocessing such as abnormality processing, bug correction and/or noisecancellation may be performed. Various aspects of the map matchingtechnology are known, which will not be detailed here to avoid confusionwith the present invention.

By mapping a plurality of locations in the trajectory to the map, aplurality of points on the map are obtained. In an embodiment, in orderto comprehensively verify an accuracy of the road network, a universalset of points on the map may be processed. Alternatively, a subset ofpoints may be selected from among the universal set of points on the mapfor processing. In other words, the set of points processed at step S210may be a particular subset of the universal set of points correspondingto the complete trajectory.

According to an embodiment of the present invention, a set of points forprocessing at step S210 is selected in various appropriate manners. Forexample, in an embodiment, after locations in the trajectory are mappedto the map, unstable points among the set of points may be located. Asan example, in an embodiment of using map matching, a match degreebetween a point and a segment can be used as a criterion for measuringthe stability of the point. In other words, a point whose match degreeis lower than a predetermined threshold may be determined as an unstablepoint. After an unstable point is determined, forward and backwardsearch may be performed along the trajectory, to find stable pointslocated before and after the unstable point, i.e., points whose matchdegree are greater than the predetermined threshold. In this way, allpoints between the two stable points may be selected for processing atstep S210.

It should be understood that the manner of selecting a set of pointsdescribed above is only exemplary, not intended to limit the scope ofthe present invention. In an alternative embodiment, a set of points tobe processed within the universal set of points corresponding to thetrajectory may also be selected in any other appropriate manner. Forexample, the set of points to be processed can be randomly selected, oreven designated by the user, etc.

For the convenience of discussion, in the context of the presentdisclosure, a first point in the set of points being processed at stepS210 is called “start point,” while the last point in the set of pointsis called “end point.” In this way, at step S210, the set of pointsbeing processed form a trajectory between a start point and an end pointon the map. It should be understood that the start point and the endpoint are only named relative to the set of points being processed or tothe trajectory. In other words, before the processed start point and/orafter the processed end point, there may be one or more pointsindicating other locations.

At step S210, dependent on different purposes of map verification, thetrajectory distance between the start point and the end point may bedetermined in a variety of different manners. For example, in oneembodiment, the trajectory distance may be a length of a route matchingthe trajectory between the start point and the end point on the map. Theterm “route” used here refers to a continuous line including one or moreroad segments. As an example, as mentioned above, the set of points maybe generated using a map matching technology. In this way, each point inthe set of points is mapped to a particular road segment in the map.These continuous road segments form a route matching the trajectory.Correspondingly, a length of the route between the start point and theend point may be computed as the trajectory distance between the startpoint and the end point. In other words, in such an embodiment, thetrajectory distance between the start point and the end point is the mapmatching distance there between.

Alternatively or additionally, in an embodiment, a polyline distancebetween the start point and the end point is be directly computed atstep S210 as the trajectory distance. Specifically, direct-linedistances of adjacent points in the set of points on the map may becomputed one by one along the trajectory, beginning from the startpoint, till the end point in the set of points. By accumulating thesedistances, the polygonal distance between the start point and the endpoint may be determined. Note, in the context of the present disclosure,a direct line is regarded as a particular type of polyline.

Next, the method 200 proceeds to step S220, where a route distance onthe map between the start point and the end point is computed. Based onthe locations of the start point and the end point represented on themap, and based on the information provided the road network of the map,one or more routes from the start point to the end point can bedetermined. In particular, if the start point and/or end point does notcompletely fall on the road segment on the map, points on the roadsegment which most match the start point and/or end point may be used asapproximates.

In an embodiment, at step S220, a length of the shortest route betweenthe start point and the end point may be computed as the route distance,the manner of seeking the shortest route is known in the art. Forexample, the Dijkstra algorithm may be used to determine the shortestroute connecting the start point and the end point on the map, and thenthe length of the route is determined as the route distance.

Besides the shortest route distance, in an embodiments, at step S220,another route between the start point and the end point may be selectedbased on any appropriate factors, and then the length of the route isdetermined as the route distance. Examples of these factors include, butare not limited to, one or more of the following: type of road segments(e.g., one-way road, express road, highway, etc.), condition of the roadsegment (e.g., number of lanes, whether there is a road segment underconstruction, etc.), real-time traffic of the road, route preference ofthe user, etc.

Next, the method 200 proceeds to step S230, where the trajectorydistance determined at step S210 and the route distance determined atstep S220 are compared to verify the road network of the map, i.e.,checking whether potential errors are present in the road network.Hereinafter, two exemplary embodiments of the step S230 will bedescribed infra with reference to FIG. 3 and FIG. 4, respectively.

FIG. 3 illustrates checking whether a road segment connectivity error ispresent in a road network of a map 300. As above mentioned, the roadsegment connectivity error means the road segment connectionrelationship on the map does not conform to the real world road segment.For example, one or more road segments on the map do not exist in thereal world at all. In the example of FIG. 3, the trajectory distancebetween the start point 310 and the end point 320 in the set of pointsis the length of the matching route. Specifically, in this example,points in the point of sets are mapped to a route 330 on the map. Asshown in the figure, the route 330 includes road segments 331-336.

In an embodiment, matching points of the start point 310 and the endpoint 320 are determined respectively. Then, the length of the route 330between the two matching points may be computed as the trajectorydistance between the start point 310 and the end point 320.

In addition, the route distance between the start point 310 and the endpoint 320 in the map 300 will also be determined. Specifically, in thisexample, the shortest route distance between the start point 310 and theend point 320 is computed. Given two points on the map and the roadnetwork information of the map, any currently existing or futuredeveloped methods may be used to calculate the shortest route distancebetween the two points.

Next, based on the trajectory distance and the shortest route distance,a detour coefficient between the start point 310 and the end point 320may be computed. The term “detour coefficient” used here represents therelationship between the trajectory distance and the shortest routedistance between the start point and the end point. For example, in anembodiment, the detour coefficient represents a ratio between thetrajectory distance and the shortest route distance. For example, theratio between the trajectory distance and the shortest route distancemay be directly used as the detour coefficient. In another embodiment,other operations (e.g., solving log, solving exponent, etc.) can also beperformed to the trajectory distance, shortest route distance and/ortheir ratio, so as to compute the detour coefficient.

According to an embodiment of the present invention, if the detourcoefficient between the start point 310 and the end point 320 is toolarge (e.g., exceeding a predetermined threshold greater than 1), it mayindicate that the actual length of the trajectory represented by the setof points is far greater than the shortest route distance between thestart point and the end point indicated in the road network of the map.In this case, it may be regarded that there likely exists a road segmenthaving a potential connectivity error between the start point 310 andthe end point 320.

The logic for such a determination lies in that if a shorter routeindicated in the road network does exist in the real world, then thevehicle or user would generally select the shorter segment to travelfrom the start point to the end point, rather than a detour. On thecontrary, if the trajectory of the user in the real world is indeed fargreater than the shortest path indicated in the road network, then oneor more road segments in the shortest road very likely do not exist inthe real world.

Specifically consider the example of FIG. 3. Suppose the road network ofthe map 300 indicates a presence of a road segment 340. Accordingly, inthis example, the shortest route from the start point 310 to the endpoint 320 includes the road segment 340. However, the actual trajectoryrepresented by the set of points advances along road segments 333, 334,and 335 instead, such that the trajectory distance is apparently greaterthan the shortest path distance indicated by the road network. In thisway, it may be determined that the road segment 340 might not exist inthe real world. In other words, road segment 340 is a road segmenthaving a connectivity error.

In an embodiment, after determining that a potential error (which isroad segment connectivity error in this example) exists between thestart point 310 and the end point 320 in response to a too large detourcoefficient, a range of the potential error on the map may be estimatedby adjusting the set of points. For example, in an embodiment, a pointafter the start point 310 in the set of points may be selected as a newstart point, and/or a point before the end point 320 in the set ofpoints may be selected as a new end point, repeating steps S210 to S230,till between which two points the potential road segment connectivityerror is located is determined.

FIG. 4 shows another embodiment of verifying a road network of a map.More specifically, in the example of FIG. 4, it may be verified whetherpotential road segment missing occurs in a road network of a map 400.

In this example, a polyline between a start point 410 and an end point420 in the set of points is computed as the trajectory distance betweenthe two in the map 400. Specifically, beginning from the start point410, in a sequence along the trajectory corresponding to the set ofpoints, map distances between adjacent points in the set of points arecomputed one by one. By accumulating these distances, the polylinedistance between the start point 410 and the end point 420 may beobtained as the trajectory distance.

Similar to the example of FIG. 3, in the example of FIG. 4, the shortestdistance between the start point 410 and the end point 420 may becomputed as the route distance between the two. Specifically, in thisexample, suppose the shortest route between the start point 410 and theend point 420 in the road network is route 430 including road segments431-436. Accordingly, the distance of the route 430 between the startpoint 410 and the end point 420 is used as the route distance.

Based on the trajectory distance and the shortest route distance betweenthe start point 410 and the end point 420, a detour coefficient betweenthe start point 410 and the end point 420 may be computed. In thisexample, for example, the detour coefficient is still computed as aratio between the trajectory distance (which is polyline distance now)and the shortest route distance. In such an embodiment, if the computeddetour coefficient is too small (e.g., smaller than a predeterminedthreshold less than 1), it indicates that the actual trajectory distanceis apparently smaller than the computed shortest route distance in theroad network. Therefore, it may be regarded that a potential roadsegment missing is present in the map 400.

The logic underlining such determination is that: if all road segmentsin the real world are covered in the road network of the map, the actualtrajectory distance between the start point and the end point should notbe significantly smaller than the shortest route distance between thestarting point and the end point in the road network. On the contrary,if such a condition occurs, i.e., the trajectory distance is apparentlysmaller than the shortest route distance, it indicates that some roadsegments existing in the real world are very likely not correctlyreflected in the road network of the map, i.e, the road network haspotential road segment missing.

Specifically consider the example of FIG. 4, road segment 440 might be amissing road segment. In other words, the road segment 440 is present inthe real world, but not correctly reflected in the road network of themap. In this case, when computing the shortest route based on the roadnetwork information, road segments 433, 434, and 435 will be chosen. Asa result, the shortest route distance computed based on the road networkinformation is significantly greater than the trajectory distance.

Similar to the example of FIG. 3, in the example shown in FIG. 4, oncethe road network of the map 400 is verified to have a potential error(in this example, it is road segment missing), a range of the potentialerror on the map may be further estimated by adjusting the set ofpoints. For example, in one embodiment, detour coefficients between thestart point and respective other points in the set of points may becomputed, finding a point with a sudden change of detour coefficient,thereby locating a possible range with road segment missing.

It should be noted that the methods of computing the trajectory distanceas depicted above with reference to FIGS. 3 and 4 may be used inexchange or in combination. For example, a polyline distance between thestart point and the end point can be computed as the trajectorydistance, and it is possible to determine whether the road network has apotential road segment connectivity error based on the ratio between thetrajectory distance and a route distance. Moreover, any otherappropriate manner of determining the trajectory distance is alsofeasible, and the scope of the present invention is not limited in thisaspect.

Returning to FIG. 2, according to an embodiment of the presentinvention, at step S230, it may be verified whether the road network ofthe map has either or both of the road segment connectivity error andthe road segment missing. Of course, other possible errors in the roadnetwork may also be checked based on the trajectory distance and theroute distance. The shortest route distance as described in the aboveexamples is only for the purpose of illustration. Dependent on differentcomputation manners of the detour coefficient, the longest routedistance or any other appropriate distance between the start point andthe end point may be computed, to compare with the trajectory distance.

Through the depictions above, at step S230, the trajectory distance andthe route distance between the start point and the end point may becompared to verify whether the road network of the map has a potentialerror. In an embodiment, when such potential error is detected, it maybe prompted to the user and/or a corresponding correction procedure maybe invoked. The method 200 may end after step S230.

Alternatively, in an alternative embodiment, the method 200 proceeds tostep S240, where other trajectories are used to repeat the verificationprocess from steps S210 to S230, so as to confirm whether the roadnetwork does have a potential error, thereby enhancing the credibilityof the verification. Specifically, suppose the map is verified to have apotential error such as a potential road segment connectivity errorand/or road segment missing at step S230. In this case, at step S240, atleast one further trajectory within relevant area of the map andcorresponding to at least one further set of points may be obtained. Forexample, in an embodiment, the selected further set of points mayinclude the start point and/or end point as previously processed or apoint nearby. Location data corresponding to such a set of points may becollected by a positioning device of other vehicle or user travelingalong a corresponding trajectory. These additional set of points may beused to repeat the road network verification procedure from step S210 tostep S230.

In this way, error check caused by some exceptions can be reduced. Forexample, consider the example of FIG. 3. If the detour coefficient ofone trajectory is far greater than 1, the possibility cannot be excludedthat road segment 340 does exist. For example, the vehicle or userlikely intentionally detoured along road segments 333, 334 and 335 dueto special reasons, without travelling along the road segment 340. Inthis case, detour coefficients may be computed for multiple times usingthe sets of points corresponding to one or more trajectories from thestart point 310 and the end point 320. If most detour coefficients aregreater than 1, it may be determined more reliably that the road segment340 is very likely an over-connected road segment that does not exist.

Alternatively or additionally, in an embodiments, the method 200proceeds to step S250, where a result of map verification is confirmedusing other trusted road network(s). The trusted road network is onethat has been verified to include correct road segment information. Forexample, in an embodiment, the trusted road network is provided by acommercial map. Alternatively, the trusted road network may be input ordesignated by the user.

Specifically, at step S250, the set of points may be mapped to thetrusted road network, and the route distance between the start point andthe end point in the trusted road network is determined as “trustedroute distance.” As an example, the shortest route distance between thestart point and the end point in the trusted road network may becalculated as “trusted shortest route distance.” Additionally, theshortest route distance between the start point and the end point in theroad network of the distance under verification may be calculated andcompared with the trusted shortest route distance. If the differencederived from the comparison is greater than the predetermined threshold,it may be confirmed that the road network of the map under verificationindeed has an error. In this case, it may be prompted to the user and/orthe road network of the map under verification may be corrected based onthe trusted road network.

It should be noted that the sequences of respective steps in FIG. 2 areonly schematic. For example, determining the trajectory distance at stepS210 and the shortest route distance at step S220 may be performed in areverse order or in parallel. For another example, determinations atsteps S240 and S259 can also be performed according to any appropriateorder.

FIG. 5 shows a schematic block diagram of a system 500 for verifying aroad network of a map according to an embodiment of the presentinvention. As shown in the figure, the system 500 includes a trajectorydistance determining unit 510 configured to determine, based onlocations of a set of points in the map, a trajectory distance of atrajectory between a start point and an end point in the set of pointson the map; a route path determining unit 520 configured to determine aroute distance between the start point and the end point in the roadnetwork of the map; and a road network verifying unit 530 configured toverify the road network by comparing the trajectory distance and theroute distance.

In an embodiment, the set of points is obtained by mapping sensedlocation data on the map using map matching. In this embodiment, thesystem 500 includes a point selecting unit configured to select at leastone of the start point and the end point from the set of points based onmatching degrees between the set of points and road segments in the roadnetwork.

In an embodiment, the trajectory distance determining unit 510 includesa matching route determining unit configured to determine a route in theroad network that matches the trajectory; and a route distancedetermining unit configured to determine a route distance of the routebetween the start point and the end point, as the trajectory distance.In this embodiment, the road network verifying unit 530 includes aconnectivity error detecting unit configured to determine, in responseto a ratio between the trajectory distance and the route distance beinggreater than a predetermined threshold, that the road network has apotential road segment connectivity error.

Alternatively or additionally, in an embodiment, the trajectory distancedetermining unit 510 includes a polyline distance determining unitconfigured to determine, as the trajectory distance, a polyline distancebetween the start point and the end point on the map by accumulatingdistances between adjacent points in the set of points along thetrajectory on the map. In this embodiment, the road network verifyingunit may include a road segment missing detecting unit configured todetermine, in response to a ratio between the trajectory distance andthe route distance being less than a predetermined threshold, that theroad network has a potential road segment missing.

In an embodiment, the system 500 may also include an error rangedetermining unit configured to determine, in response to the roadnetwork being verified to have a potential error, a range of thepotential error on the map by adjusting the set of points.

In an embodiment, the system 500 may further include a first confirmingunit configured to repeat, in response to the road network beingverified to have a potential error, the verifying of the road networkusing at least one further trajectory corresponding to at least onefurther set of points on the map, to confirm the potential error in theroad network.

In an embodiment, the system 500 may also include a trusted distancedetermining unit configured to determine, in response to the roadnetwork being verified to have a potential error, a trusted routedistance between the start point and the end point in the road network;a distance comparing unit configured to compare the route distance andthe trusted route distance, and a second confirming unit configured toconfirm the potential error in the road network of the map based on thecomparing.

It should be noted that for the sake of clarity, FIG. 5 does not showoptional units or sub-units included in the system 500. All features andoperations as described above are suitable for system 500, respectively,which are therefore not detailed here. Moreover, partitioning of unitsor subunits in system 500 is exemplary, rather than limitative, intendedto describe its main functions or operations logically. A function ofone unit may be implemented by a plurality of other units; on thecontrary, a plurality of units may be implemented by one unit. The scopeof the present invention is not limited in this aspect.

Moreover, the units included in the system 500 may be implemented byvarious manners, including software, hardware, firmware or a randomcombination thereof. For example, in some embodiments, the apparatus maybe implemented by software and/or firmware. Alternatively oradditionally, the system 500 may be implemented partially or completelybased on hardware. for example, one or more units in the system 500 maybe implemented as an integrated circuit (IC) chip, anapplication-specific integrated circuit (ASIC), a system on chip (SOC),a field programmable gate array (FPGA), etc. The scope of the presentintention is not limited to this aspect.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may includecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein includes anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which includes one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

1. A computer implemented method for verifying a road network of a map, the method comprising: determining, by a trajectory distance determining unit, based on locations of a set of points in the map, a trajectory distance of a trajectory between a start point and an end point in the set of points on the map; determining a route distance between the start point and the end point in the road network of the map; verifying the road network by comparing the trajectory distance to the route distance, wherein verifying the road network further comprises, determining that the road network has a potential road segment missing, in response to a ratio between the trajectory distance and the route distance being less than a first predetermined threshold; confirming results of verifying the road network by comparing a shortest route distance between the start point and the end point of the road network to a trusted shortest route distance of a trusted road network; and prompting a user of an error in the road network of the map, based on the comparison of the shortest route distance to the trusted shortest route distance.
 2. The computer implemented method according to claim 1, wherein determining a trajectory distance of a trajectory between a start point and an end point in the set of points on the map comprises: determining a route in the road network that matches the trajectory; and determining a route distance of a route between the start point and the end point as the trajectory distance.
 3. The computer implemented method according to claim 1, wherein verifying the road network by comparing the trajectory distance and the route distance comprises: in response to a ratio between the trajectory distance and the route distance being greater than a second predetermined threshold, determining that the road network has a potential road segment connectivity error.
 4. The computer implemented method according to claim 1, further comprising: determining, in response to the road network being verified to have a potential error, a range of the potential error on the map by adjusting the set of points.
 5. The computer implemented method according to claim 1, further comprising: repeating, in response to the road network being verified to have a potential error, the verifying of the road network using at least one further trajectory corresponding to at least one further set of points on the map to confirm the potential error in the road network.
 6. The computer implemented method according to claim 1, further comprising: determining, in response to the road network being verified to have a potential error, a trusted route distance between the start point and the end point in the road network; comparing the route distance and the trusted route distance; and confirming the potential error in the road network of the map based on the comparison.
 7. A computer program product for verifying a road network of a map, the method comprising: one or more computer-readable storage media and program instructions stored on the one or more computer-readable storage media, the program instructions comprising: program instructions to determine, based on locations of a set of points in the map, a trajectory distance of a trajectory between a start point and an end point in the set of points on the map; program instructions to determine a route distance between the start point and the end point in the road network of the map; program instructions to verify the road network by comparing the trajectory distance to the route distance, wherein the program instructions to verify the road network further comprises, program instructions to determine that the road network has a potential road segment missing, in response to a ratio between the trajectory distance and the route distance being less than a first predetermined threshold; program instructions to confirm results of verifying the road network by comparing a shortest route distance between the start point and the end point of the road network to a trusted shortest route distance of a trusted road network; and program instructions to prompt a user of an error in the road network of the map, based on the comparison of the shortest route distance to the trusted shortest route distance.
 8. The computer program product according to claim 7, wherein the program instructions to determine a trajectory distance of a trajectory between a start point and an end point in the set of points on the map comprises: program instructions to determine a route in the road network that matches the trajectory; and program instructions to determine a route distance of a route between the start point and the end point as the trajectory distance.
 9. The computer program product according to claim 7, wherein the program instructions to verify the road network by comparing the trajectory distance and the route distance comprises: in response to a ratio between the trajectory distance and the route distance being less than a second predetermined threshold, program instructions to determine that the road network has a potential road segment missing.
 10. The computer program product according to claim 7, further comprising: program instructions to determine, in response to the road network being verified to have a potential error, a range of the potential error on the map by adjusting the set of points.
 11. The computer program product according to claim 7, further comprising: program instructions to repeat, in response to the road network being verified to have a potential error, the verifying of the road network using at least one further trajectory corresponding to at least one further set of points on the map to confirm the potential error in the road network.
 12. The computer program product according to claim 7, further comprising: program instructions to determine, in response to the road network being verified to have a potential error, a trusted route distance between the start point and the end point in the road network; program instructions to compare the route distance and the trusted route distance; and program instructions to confirm the potential error in the road network of the map based on the comparison.
 13. A computer system for verifying a road network of a map, the computer system comprising: one or more computer processors, one or more computer-readable storage media, and program instructions stored on the one or more of the computer-readable storage media for execution by at least one of the one or more processors, the program instructions comprising: program instructions to determine, based on locations of a set of points in the map, a trajectory distance of a trajectory between a start point and an end point in the set of points on the map; program instructions to determine a route distance between the start point and the end point in the road network of the map; program instructions to verify the road network by comparing the trajectory distance to the route distance, wherein the program instructions to verify the road network further comprises program instructions to determine that the road network has a potential road segment missing, in response to a ratio between the trajectory distance and the route distance being less than a first predetermined threshold; program instructions to confirm results of verifying the road network by comparing a shortest route distance between the start point and the end point of the road network to a trusted shortest route distance of a trusted road network; and program instructions to prompt a user of an error in the road network of the map, based on the comparison of the shortest route distance to the trusted shortest route distance.
 14. The computer system according to claim 13, wherein the program instructions to determine a trajectory distance of a trajectory between a start point and an end point in the set of points on the map comprises: program instructions to determine a route in the road network that matches the trajectory; and program instructions to determine a route distance of a route between the start point and the end point as the trajectory distance.
 15. The computer system according to claim 13, wherein the program instructions to verify the road network by comparing the trajectory distance and the route distance comprises: in response to a ratio between the trajectory distance and the route distance being less than a second predetermined threshold, program instructions to determine that the road network has a potential road segment missing.
 16. The computer system according to claim 13, further comprising: program instructions to determine, in response to the road network being verified to have a potential error, a range of the potential error on the map by adjusting the set of points.
 17. The computer system according to claim 13, further comprising: program instructions to repeat, in response to the road network being verified to have a potential error, the verifying of the road network using at least one further trajectory corresponding to at least one further set of points on the map to confirm the potential error in the road network.
 18. The computer system according to claim 13, further comprising: program instructions to determine, in response to the road network being verified to have a potential error, a trusted route distance between the start point and the end point in the road network; program instructions to compare the route distance and the trusted route distance; and program instructions to confirm the potential error in the road network of the map based on the comparison. 